There has been a long-felt need for electrical receptacles or outlets which are safer; especially for children. Conventional electrical receptacles allow several possibly dangerous situations to occur. One situation results from foreign objects such as paper clips or car keys inserted into the receptacle. If the object is conductive, the person holding the foreign object acts as a conductor, thereby permitting current to flow through the object and through the person. This situation is more likely among children. While adults know better than to insert foreign objects into a receptacle, they are nevertheless not immune to the possible dangers. Adults can receive a shock by improperly holding or grasping the plug while inserting or removing it from the receptacle, since it is possible to make contact with one or more of the conducting blades while grasping the plug.
Conventional house electrical systems operate at about 110-120 volts, which is sufficient to possibly cause serious damage. Children are especially vulnerable to the effects of electricity. Consequently, a need has been recognized for safer electrical receptacles.
Some of the more common solutions in the past have utilized mechanical structures which prevent direct insertion of foreign objects. An example includes a plastic device inserted into a receptacle. This device has a flat surface which covers the face of the receptacle and several plastic blades which fit into the receptacle, thereby holding the device firm. While in place, these plugs prevent insertion of any foreign objects into the receptacle. Unfortunately, these plugs can be removed, rendering their safety efficacy nonexistent. If not removed, they present an obstacle to adults who wish to use the receptacle.
Another solution replaces the receptacle cover with a device which prevents direct insertion. One style requires the user to partially insert the plug into the receptacle, and then rotate 90xc2x0 to gain insertion. Another style includes the same partial insertion step, but requires a subsequent lateral translation to gain complete insertion. These structures can""t completely prevent insertion of foreign objects, and can be ungainly as they are mounted in front of the receptacle in place of a conventional receptacle cover.
Other solutions include mechanical switching within a modified receptacle. For example, an inserted plug can have one or more blades that can activate such a switch. Alternatively, the receptacle can require use of a modified plug which contains one or more pins for switch activation. These solutions, unfortunately, include mechanical moving parts which are prone to wear or require the user to replace the plugs on all electrical devices. Further each of these possible solutions require user interaction. Typically, if a user is required to perform additional steps to operate a modified receptacle, they will often not bother and will eventually replace the modified receptacle with a standard outlet.
Another solution includes the use of optics; specifically, a light beam which can be interrupted by plug insertion. Typically, no power would flow while the light beam is uninterrupted, indicating that no plug is present. When a plug is inserted, the light beam is interrupted and power is allowed to flow. This solution may assist in preventing shocks caused by improperly held plugs (since the plug may need to be completely inserted to block the light beam, the user is unable to make contact with the plug blades). Unfortunately, any inserted object of a particular minimum size will block the light beam and permit power to flow. While this avoids the complexity of moving mechanical parts, insertion of most foreign objects would permit current to flow. This solution lacks the sophistication necessary to provide a receptacle which is safe for both children and adults.
A substantial need remains for electrical receptacles which are safe for children yet easy for adults to use. Preferably, such an electrical receptacle would also have the ability to prevent shocks caused by partial plug insertion.
Accordingly, the invention includes an electrical receptacle which is safe for children yet is easy for adults to use. A novel combination of sensors and circuitry within the receptacle prevent shocks caused by insertion of foreign objects and by improperly grasping a partially inserted plug. The receptacle has one or more plug component sensors that can detect blade insertion, ground prong insertion, presence of the plug face, motion near the receptacle face, or a combination thereof.
The electrical receptacle of the invention can include a plurality of plug component sensors for the purpose of determining the presence or absence of specific geometric features of a standard plug. Examples of plug component sensors include a blade sensor, a ground prong sensor and a face sensor. The electrical receptacle of the invention can utilize any combination of these sensors. Each plug component sensor reports the proximal presence or absence of a plug component or foreign object in the space occupied by the plug component in a properly inserted condition.
In one embodiment, the receptacle of the invention includes a contact assembly, a relay assembly, an LED, a photodetector, a plug component sensor and a control circuit. The contact assembly is adapted and configured to selectively and conductively couple each blade of the plug to the relay assembly while the relay assembly is adapted and configured to conductively couple the contact assembly to conductors. Preferably, the plug component sensor includes a diffuse reflective sensor including the LED and the photodetector; wherein the LED emits light which is reflected by a component of a properly inserted plug and is detected by the photodetector, thereby signaling the control circuit to provide power to the properly inserted plug. A properly inserted plug is defined as one which is completely inserted into the receptacle; thereby permitting power to flow to the plug without risking shock caused by contact with a partially inserted plug.
The invention also includes an electrical receptacle having two or more plug component sensors. In one -embodiment including a control circuit, this permits a control circuit to determine if substantially simultaneous insertion has occurred. Plug geometry requires that a properly inserted plug will present any individual components such as blades and ground prongs at virtually the same time. If individual sensors detect time delayed insertion, it is likely that one or more foreign objects have been inserted. In that situation, the control circuit would not permit power to flow. Substantially simultaneous detection of component insertion can be required to cause power to flow.
The electrical receptacle of the invention includes a contact assembly, which is adapted and configured to conductively couple each blade of the plug to a conductor. For this invention, the electrical state of the contact assembly is determined by the relays, as the contact assembly is conductively coupled to (a) relay(s).
The electrical receptacle of the invention includes a control circuit which determines presence of a properly inserted plug, and may also ensures no activity in the immediate vicinity of the plug, or other features of the receptacle""s environment. The electrical receptacle of the invention can utilize any combination of the plug component sensors and any signal analysis method(s). Electrical control which requires substantially simultaneous detection of two or more plug components virtually eliminates the possibility of accidental shock or electrocution as a result of inserting foreign objects.